Optical data communication systems commonly include optical receiver devices that receive optical signals conveyed via an optical communication link (e.g., optical fiber) and convert the optical signals into electrical signals. In this manner, the data or information contained in the optical signals can be recovered or received and provided to other electronic systems, such as switching systems or processing systems. Such optical receiver devices include photodetectors, such as photodiodes. A common type of photodiode used in optical receiver devices is known as a PIN photodiode due to its structure comprising an intrinsic or lightly doped semiconductor layer sandwiched between a P-type semiconductor layer and an N-type semiconductor layer. PIN diode physics dictate that the size of the active area (i.e., photosensitive area) is inversely proportional to the maximum data rate that the device can detect. Thus, a PIN photodiode suitable for high data rates must have a small active area. However, the light emitted by an optical fiber forms a beam that is relatively wide compared with the width of a high-speed PIN photodiode. Focusing or otherwise directing the incoming light (optical signals) onto a very small PIN photodiode poses design challenges.
An optical receiver can include a lens between a PIN photodiode device and an end of an optical fiber to focus light emitted from the fiber onto the PIN photodiode. However, including such a lens in an optical receiver can impact ease of assembly and thus manufacturing economy. It has also been suggested to fashion a region of the semiconductor substrate from which the PIN photodiode is formed into a reflector that directs light into the active area of a PIN photodiode from a lateral direction, i.e., parallel to the plane of the substrate. However, such a structure is difficult to fabricate and thus impacts manufacturing economy. Moreover, such a structure is generally incapable of increasing the light-collecting area of the PIN photodiode device by more than a few microns.
It would be desirable to provide a photodetector device that has a large collection area relative to the size of the active area and that can be readily manufactured.